package test2;

import java.util.Stack;
//用栈实现队列
public class demo2 {
    class MyQueue {
        private Stack<Integer> s1;
        private Stack<Integer> s2;

        public MyQueue() {
            s1 = new Stack<>();
            s2 = new Stack<>();
        }

        public void push(int x) {
            s1.push(x);
        }

        public int pop() {
            if(empty())
            {
                return -1;
            }
            if(s2.isEmpty())
            {
                while(!s1.isEmpty())
                {
                    s2.push(s1.pop());
                }
            }

            return s2.pop();
        }

        public int peek() {
            if(empty())
            {
                return -1;
            }
            if(s2.isEmpty())
            {
                while(!s1.isEmpty())
                {
                    s2.push(s1.pop());
                }
            }
            return s2.peek();
        }

        public boolean empty() {
            return s1.isEmpty()&& s2.isEmpty();
        }
    }

}
